This invention is directed to a transparent silicone, and more particularly to a ternary composition of water, a volatile cyclic or linear methyl siloxane (VMS), and a short-chain or low molecular weight silicone polyether, which when combined provide an optically clear gel.
It is well documented (i.e., U.S. Pat. No. 4,999,398) that emulsions, especially silicone emulsions, are opaque, cloudy, and tend to separate on standing. Thus, the desirability of microemulsions which contain micro-particles in the droplet phase providing a measure of clarity, or gels which are thermodynamically stable transparent structures.
As used herein, the term emulsion or macroemulsion means a dispersion of one immiscible liquid in another, in the form of droplets with diameters approximately in the range of 100-1,000 nanometers (0.1-1.0 microns/1,000-10,000 angstroms .ANG.).
In contrast, a microemulsion means a transparent dispersion of two or more immiscible liquids and a surfactant. Microemulsions are clear or transparent because they contain particles smaller than the wavelength of visible light, which is typically on order of about 10-100 nanometers.
Microemulsions may contain oil droplets dispersed in water (O/W), water droplets dispersed in oil (W/O), or they may be in the form of a bi-continuous structure. They are characterized by an ultra-low interfacial tension between the oil and water phases.
A microemulsion can be recognized by several of its inherent characteristics which are that (i) it contains oil, water, and a surfactant; (ii) there is a high concentration of surfactant relative to oil; (iii) the system is optically clear; (iv) the phases do not separate by centrifugation; and (v) the system forms spontaneously.
Thus, as used herein, an emulsion is considered as containing particles having an average diameter of more than 100 nanometers (0.1 microns/1,000 angstroms .ANG.), whereas a microemulsion is considered as containing particles having an average diameter of less than 100 nanometers (0.1 microns/1,000 angstroms .ANG.).
Clarity or transparency is controlled to a great extent by the particle size of the dispersed phase. The scattering of light is dependent on the particle size. Therefore, clear or transparent compositions appear to be a single phase without droplets or particles when viewed with the naked eye.
On the other hand, and in contrast to an emulsion or microemulsion, a gel is a semi-solid stabilized or set by a three-dimensional lattice system. Because a surfactant has a bipolar amphiphilic structure (i.e., a water-soluble polar head and a water-insoluble organic tail), surfactant molecules accumulate preferentially at the interface of two immiscible phases. If the concentration at the interface exceeds the critical micelle forming concentration (cmc), a colloidal surfactant solution is produced. With increasing concentration, or volume fraction of the internal phase, such a solution becomes a structured gel.
Bailey in U.S. Pat. No. 3,299,112 describes products formed from a ternary system of water, a silicone oil, and a silicone polyether. But in contrast to my invention, the products in Bailey are emulsions which are not clear; the ternary system in the '112 patent is not a gel; the silicone oil in Bailey is not a volatile cyclic VMS; and where Bailey does describe a linear silicone oil, it is not a volatile linear silicone oil.
Rather, the silicone oil in Bailey corresponds to R".sub.3 SiO(R".sub.2 SiO).sub.x SiR".sub.3 where x is 10-1,000. My corresponding volatile linear VMS have an "x" of 0-5, well below the range in Bailey. In fact, where "x" exceeds 5, products tend not to be clear.
Furthermore, emulsions as in Bailey are recognized as inherently unstable systems separating with time. In contrast, my gels are stable indefinitely. The order of addition of the components does influence their formation, and with mild mixing at room temperature (20.degree.-25.degree. C./68.degree.-77.degree. C.), that is sufficient to cause stable gels to form.
My clear gel has particular value in the personal care arena. Because of the unique volatility characteristics of the VMS component of my ternary system, it can be used alone, or blended with other cosmetic fluids to form a variety of over-the-counter personal care products.
Thus, it is useful as a carrier in antiperspirants and deodorants, since it leaves a dry feel, and does not cool the skin upon evaporation. It is lubricious and will improve the properties of skin creams, skin care lotions, moisturizers, facial treatments such as acne or wrinkle removers, personal and facial cleansers, liquid soaps, bath oils, perfumes, colognes, sachets, sunscreens, pre-shave and after-shave lotions, shaving soaps, and shaving lathers. It can be used in hair shampoos, hair conditioners, hair sprays, mousses, permanents, depilatories, and cuticle coats, to enhance gloss and drying time, and provide conditioning benefits.
In cosmetics, it will function as a leveling and spreading agent for pigments in make-ups, color cosmetics, foundations, blushes, lipsticks, lip balms, eyeliners, mascaras, oil removers, color cosmetic removers, and powders. It is also useful as a delivery system for oil and water soluble substances such as vitamins. When incorporated into sticks, other gels, lotions, aerosols, and roll-ons, my ternary composition imparts a dry, silky-smooth, pay-out.
Additionally, my clear gel exhibits a variety of advantageous and beneficial properties such as (i) clarity, (ii) the ability to combine properties of water and oil in a single homogeneous material, (iii) shelf stability, and (iv) ease of preparation; and consequently it has wide application but especially in cosmetics or antiperspirants.
A transparent gel for cosmetic or antiperspirant uses should be semi-solid materials at rest, but should thin sufficiently under moderately applied shear stress, to flow easily and smoothly when spread over the skin.
Beyond personal care, the gels have application in formulating consumer products such as ski waxes, insecticides, stain removal sticks, car waxes, tire treatments, and vinyl protectants.